| Summary: | 碩士 === 高雄醫學大學 === 醫學研究所 === 89 === Lung cancers are a leading cause of cancer-related death in Taiwan. They can be divided into two groups, small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC), according to their histological features. The poor prognosis of lung cancers may be partically based on the pronounced resistance to chemotherapeutic drugs. TA303, was isolated from a Chinese herb. The cytotoxicity of TA303 was determined by MTS method. Comparing to other antitumor drugs, e.g. MTX, 5-FU, Cyclophosphamide, Etoposide, Gemcitabine, Cisplatin and Epirubicin, TA303 possessed the highest cytotoxicity, with IC50 were 20mM and 24.18mM for human lung adenocarcinoma (H441) and squamous cell carcinoma (H520), respectively. The maximum death of H441 and H520 were determined in 10 h after TA303 treatment , and no increase death of these two cell lines was observed for an extent-incubation of 16 hr, suggesting that the action of TA303 on H441 and H520 was irreversible. The synergistic effects of TA303 combined therapy with Cisplatin and Epirubicin and TA303 on H441 and H520 cells were eualuated. The combination of Cisplatin and Epirubicin with TA303 increases the cytotoxicity to the cell.
In order to define the action mechanism of TA303 on H441 and H520, the morphological changes, DNA content, and gene expression of the cells after TA303 treatment were analyzed. The appearances of chromatin condensation was observed after treatment with high dose of TA303 (36 mM) for 2 hr, and apoptotic bodies in cells were observed for 5 hr. The sub-G1 peak of TA303-treated H441 and H520 cells were was shown to determined by flow cytometry. The results indicate that TA303 induced cell death by apoptosis.
To define the apoptotic mechanism of TA303 on H441 and H520 cells, the change of gene expression after TA303 treatment was studied. A significant up-regulations of TNFR、Fas as well as TRAIL-R gene expression for H520, and TNFR as well as TRAIL-R for H441 cell were observed. The TA303-mediated cytotoxicity could be neutralized by Fas and TNF receptor’s specific antibodies, and the synergistic cytotoxicity effect was appearance after TRAIL-R antibodies treatment. The caspase-3 was also activated after TA303 treatment. These results indicated that over expression TNFR and TRAIL-R might be involved in TA303-induced apoptosis of human adenocarcinoma and squamous cell carcinoma. After establishing significant cytotoxicity to TA303 in vitro, human lung adenocarcinoma xenografts (in vivo) were then treated with TA303 resulted in significantly greater growth inhibition.
In conclusion, TA303 might induce cell apoptosis of human lung adenocarcinoma and squamous cell carcinoma cell by triggering TNF superfamily, and the growth of human lung adenocarcinoma xenografts in nude mice was significantly inhibited after several cycles of TA303 treatment. This study demonstrates the action mechanism of TA303, and may shed light on the investigation of Chinese herbs as new chemotherapeutic agents for clinical cancer therapy.
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